a) Field of the Invention
This invention relates to an elastic-tube-operated brake band suitable for use in an automatic transmission, brake or the like.
b) Description of the Related Art
For binding a brake band in a brake, it is the common practice to press a bracket attached to an end of a strap. The bracket is however subjected to localized force. The brake band of this type is therefore accompanied by an inconvenience that any attempt to enhance the strength of the bracket leads to an increase in manufacturing cost.
An apparatus was hence contemplated such that pressure can be applied by charging pressure fluid into a tube arranged between an inner member and an outer member and inflating the tube. In this design, however, the tube is required to have substantial strength as torques are borne by the tube itself. The tube must therefore be provided with a significant thickness, leading to an inconvenience in that the brake band cannot avoid a dimensional increase.
To solve the above-described inconvenience, it was then contemplated to arrange a strap, which carries a friction material bonded on an inner circumferential surface thereof, between the tube and the inner member.
FIG. 8 is a cross-sectional view, which illustrates the above-mentioned conventional elastic-tube-operated brake band at numeral 10. FIG. 8 shows an outer frame 20, a folded portion 21 of the outer frame 20, a pressure fluid supply hole 22 of an elastic tube 40, a ring-shaped strap 30, a folded portion 31 of the strap 30, a bolt 32 connecting the outer frame 20 and the folded portion 31 of the strap 30 with each other, a friction material 50 bonded on an inner circumferential surface of the strap 30, and a void space 60 which should be occupied by an unillustrated counterpart to be bound, namely, an inner member (for example, a drum). The strap is folded at opposite ends thereof to prevent the tube 40 from bulging out into direct contact with the counterpart when the tube 40 is inflated.
In the above-described conventional brake band, force is not applied directly to the tube 40 but is applied to the tube 40 via the strap 30. This has made it possible to eliminate a circumferential load which would otherwise be applied from the counterpart to the tube. The strap 30 is however fixed at only one end thereof on the outer frame 20, resulting in a drawback that in the illustrated case, self-engaging force can be produced between the strap and the inner member only when a torque acts counterclockwise.